5 ms·

I'm deeply missing hot swapping. I believed it could be included in java 9 but i think we have to wait...

by haddr 12y ago

curiousCoffee 12y ago
What is hot swapping?
- ZoFreX 12y ago
  Replacing code while it's running. Currently this is possible but quite limited in the official JDK, you can only replace the contents of method bodies. Edit: Demo of it in action here, notch is rapidly developing a game in Eclipse by changing the code while it's running: https://www.youtube.com/watch?v=rhN35bGvM8c https://www.youtube.com/watch?v=rhN35bGvM8c
  - exabrial 12y ago
    There's always JRebel!
    - pjmlp 12y ago
      Not really. http://zeroturnaround.com/blog/goodbye-liverebel/ http://zeroturnaround.com/blog/goodbye-liverebel/
      - curiousCoffee 12y ago
        Oh, damn! I just started using jrebel.. (I know I asked what hotswapping was but I was curious if the OP meant hotswapping in the same way as jrebel or something else) edit: Wait, that is liverebel, not jrebel
        pjmlp 12y ago
        Ah, sorry! I though liverebel was the new name.
  - andor 12y ago
    notch is rapidly developing a game in Eclipse He's modifying the Swing object tree from the main thread! Don't do that, Swing isn't thread safe ;-) https://www.youtube.com/watch?v=rhN35bGvM8c#t=1454 https://www.youtube.com/watch?v=rhN35bGvM8c#t=1454 http://docs.oracle.com/javase/7/docs/api/javax/swing/package-summary.html#threading http://docs.oracle.com/javase/7/docs/api/javax/swing/package...
exelius 12y ago
Isn't this basically what Spring is for? I get that it's not included in the language itself, but that seems more like a feature that should be provided by a framework rather than the language itself...
- tootie 12y ago
  No, that's not part of Spring. It would be implemented by a container. OSGi was a sort of failed attempt at standardizing it. Right now you have to pay for something like jrebel (worth it, IMO) to get hot swapping.
mdaniel 12y ago
Are you aware of DCEVM? https://github.com/DCEVM/DCEVM#readme https://github.com/DCEVM/DCEVM#readme
einrealist 12y ago
What is wrong with restarting your application? Edit: Real Hotswapping will requires profound changes to the memory model. It would introduce too much complexity. I rather restart my application than to suffer from a fragile and leaking platform.
- tieTYT 12y ago
  It can take up to 5 minutes to restart my application.
  - einrealist 12y ago
    Can't you just break things up to see them in action? If not, you should question your architecture.
  - Roboprog 12y ago
    So run multiple instances of the app, and put some kind of load balancer / proxy in front of the instances. Unfortunately, this will require externalization of state data, but if you can't be down for 5 minutes, that's what you need to do. You probably only need one large server running the instances, rather than a cluster. Java apps don't seem to do well -- longer GC pauses -- when they have over 2 GB of memory, anyway, so run multiple instances of "small" apps on a server with say 12 cores. A single server with a large pool of RAM shared between a large number of cores can do pretty amazing things with a collection of "small" programs on it (DB, web service apps, message queue server, web servers) Of course, I'm assuming said server isn't Windows...
    - winterbe 12y ago
      I don't think he meant hotswapping in productive environments but during development. Load balancing doesn't help here. The webapp I'm working on currently has a startup time of 50s on my macbook. If I restart the webapp 100 times a day, thats a total waiting time of 30+ minutes. Our team is 6 developers, so we loose 3h per day. Real hotswapping may be extremely complex but IMO it would be absolutely worth the effort.
karianna 12y ago
ZeroTurnaround have a payware product (that's highly acclaimed in this space) called JRebel. It swaps out bytecode directly as opposed to using Java's (somewhat broken) classloader mechanism.

I'm deeply missing hot swapping. I believed it could be included in java 9 but i think we have to wait...

by haddr 12y ago

I'm deeply missing hot swapping. I believed it could be included in java 9 but i think we have to wait...

curiousCoffee 12y ago

What is hot swapping?

ZoFreX 12y ago
Replacing code while it's running. Currently this is possible but quite limited in the official JDK, you can only replace the contents of method bodies. Edit: Demo of it in action here, notch is rapidly developing a game in Eclipse by changing the code while it's running: https://www.youtube.com/watch?v=rhN35bGvM8c https://www.youtube.com/watch?v=rhN35bGvM8c
- exabrial 12y ago
  There's always JRebel!
  - pjmlp 12y ago
    Not really. http://zeroturnaround.com/blog/goodbye-liverebel/ http://zeroturnaround.com/blog/goodbye-liverebel/
    - curiousCoffee 12y ago
      Oh, damn! I just started using jrebel.. (I know I asked what hotswapping was but I was curious if the OP meant hotswapping in the same way as jrebel or something else) edit: Wait, that is liverebel, not jrebel
      - pjmlp 12y ago
        Ah, sorry! I though liverebel was the new name.
- andor 12y ago
  notch is rapidly developing a game in Eclipse He's modifying the Swing object tree from the main thread! Don't do that, Swing isn't thread safe ;-) https://www.youtube.com/watch?v=rhN35bGvM8c#t=1454 https://www.youtube.com/watch?v=rhN35bGvM8c#t=1454 http://docs.oracle.com/javase/7/docs/api/javax/swing/package-summary.html#threading http://docs.oracle.com/javase/7/docs/api/javax/swing/package...

exelius 12y ago

Isn't this basically what Spring is for? I get that it's not included in the language itself, but that seems more like a feature that should be provided by a framework rather than the language itself...

tootie 12y ago
No, that's not part of Spring. It would be implemented by a container. OSGi was a sort of failed attempt at standardizing it. Right now you have to pay for something like jrebel (worth it, IMO) to get hot swapping.

mdaniel 12y ago

Are you aware of DCEVM? https://github.com/DCEVM/DCEVM#readme https://github.com/DCEVM/DCEVM#readme

einrealist 12y ago

What is wrong with restarting your application? Edit: Real Hotswapping will requires profound changes to the memory model. It would introduce too much complexity. I rather restart my application than to suffer from a fragile and leaking platform.

tieTYT 12y ago
It can take up to 5 minutes to restart my application.
- einrealist 12y ago
  Can't you just break things up to see them in action? If not, you should question your architecture.
- Roboprog 12y ago
  So run multiple instances of the app, and put some kind of load balancer / proxy in front of the instances. Unfortunately, this will require externalization of state data, but if you can't be down for 5 minutes, that's what you need to do. You probably only need one large server running the instances, rather than a cluster. Java apps don't seem to do well -- longer GC pauses -- when they have over 2 GB of memory, anyway, so run multiple instances of "small" apps on a server with say 12 cores. A single server with a large pool of RAM shared between a large number of cores can do pretty amazing things with a collection of "small" programs on it (DB, web service apps, message queue server, web servers) Of course, I'm assuming said server isn't Windows...
  - winterbe 12y ago
    I don't think he meant hotswapping in productive environments but during development. Load balancing doesn't help here. The webapp I'm working on currently has a startup time of 50s on my macbook. If I restart the webapp 100 times a day, thats a total waiting time of 30+ minutes. Our team is 6 developers, so we loose 3h per day. Real hotswapping may be extremely complex but IMO it would be absolutely worth the effort.

karianna 12y ago

ZeroTurnaround have a payware product (that's highly acclaimed in this space) called JRebel. It swaps out bytecode directly as opposed to using Java's (somewhat broken) classloader mechanism.